In modern society there is a great deal of emphasis on the appearance and manageability of hair. For example, over time, human hair acquires a dirty look and feel as a result of its contact with the atmosphere and as a result of sebum secreted by the head. Therefore, conformity with current societal norms requires that the hair be kept clean, and shampooed regularly. However, in practice, the tendency is for individuals to shampoo their hair daily.
Shampooing the hair cleans by removing excess soil and sebum. However, the shampooing process often leaves the hair in a tangled and generally unmanageable state. To improve the manageability of washed hair, conditioning aids were developed such as hair rinses. Initially such conditioning aids were applied to the hair following the step of shampooing the hair. However, there are disadvantages associated with such conditioning products.
With respect to hair rinses, they must remain on the hair for a length of time and then the hair must be rinsed with fresh water an additional time. With respect to leave-on hair conditioners, the amount of conditioner to apply is often difficult to determine based on the amount and thickness of the hair to be conditioned, and even then the uniform distribution of conditioner throughout the hair can be a problem. Therefore, to cope with the above problems it became desirable to formulate a combined shampoo and conditioner.
Although shampoos and conditioners in theory could be combined in the same product, in actuality problems arose concerning the compatibility between the detergents and the conditioners present in the product. This problem was addressed by the development of suspension agents. For example, U.S. Pat. No. 4,741,855 discloses a shampoo composition comprising a detergent, a silicone conditioner, water and a suspension agent, with choices for the suspension agent including long chain esters of ethylene glycol, and esters of long chain fatty amine oxides. However, the conditioning shampoo is not an anti-dandruff shampoo.
Still further, U.S. Pat. No. 5,015,415 discloses a conditioning shampoo comprising a certain phthalic acid and phthalic acid ammonium salts or mixtures thereof incorporated into a shampoo base with a silicone conditioner. In Cosmetics, Toiletry, and Fragrance Association (CTFA) nomenclature, phthalic acids may be designated as amido carboxy benzoic acids, and phthalic acid ammonium salts may be designated ammonium amido carboxy benzoates.
U.S. Pat. No. 4,927,563 discloses a selenium sulfide shampoo containing a mixture of xanthan gum and magnesium aluminum silicate as a suspending system. Still another known suspension system comprises xanthan gum, glycerol distearate and cetyl alcohol.
The entire matter encounters additional complications when the product is desired for use as an anti-dandruff conditioning shampoo. Typical anti-dandruff agents include colloidal or powder sulfur, coal tar derivatives, zinc pyrithione, selenium sulfide and mixtures thereof. With respect to selenium sulfide, its anti-dandruff effectiveness was established when U.S. Pat. No. 2,694,669 was awarded for an invention in a stabilized selenium disulfide therapeutic shampoo.
Although selenium sulfide is effective in controlling dandruff, its use in a shampoo, much less in a conditioning shampoo, creates additional problems. The first problem that is created concerns the stability of the shampoo. One of the constant concerns with a selenium sulfide shampoo is that the pH be kept below 6.5 during its shelf life. When the pH becomes greater than 6.5, the selenium sulfide starts to break down, with the result being that potentially toxic sulfides may be formed. The approach to that problem in the past has been to formulate the shampoo with a strongly acidic pH, and then hope that over the shelf life of the shampoo the pH does not drift above 6.5.
The second problem concerns the specific density of selenium sulfide. The high specific density of selenium sulfide makes it difficult for it to remain suspended in liquid shampoos. Selenium sulfide tends to precipitate out of solution. In the past it was found that two or more suspending agents often had to be used to overcome this problem. Examples of such suspension systems included ones comprising bentonite and magnesium aluminum silicate, or hydroxypropyl methylcellulose and magnesium aluminum silicate.
It is thus apparent that a need exists for an improved anti-dandruff conditioning shampoo containing selenium sulfide.